The Access Layer
Module 7.
Encapsulation
The process of placing one message format inside another message format is encapsulation. De-encapsulation is when the process is reversed by the recipient. Each message is encapsulated in a specific format, called a frame, before it is sent.
MAC Address Table
An Ethernet switch is used at Layer 2. When a host sends a message to another host on the same switched network, the switch decodes the frames to read the MAC address portion of the message. The MAC Address Table contains a list of all active ports and their associated host MAC addresses. When a message is received, the switch checks to see if the destination MAC is in the table, if it is, the switch starts a temporary connection (circuit) between the source and destination.
The MAC Address Table is built by examining the source MAC of each frame sent.
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